Because fever is so common in children, obtaining an accurate body temperature is helpful whenever you suspect infection, collagen vascular disease, or malignancy. The techniques for obtaining rectal, oral, and auditory canal temperatures in adults are described on pp. 81-82. Axillary and thermal-tape (temporal artery) skin temperature recordings in children are inaccurate.
In children and adolescents, auditory canal temperature recordings are preferable because they can be obtained quickly with essentially no discomfort. For infants under 2 months of age, rectal temperatures are preferred because clinical guidelines for evaluating serious bacterial infections use rectal temperature levels as a major criterion.
The technique for obtaining the rectal temperature is relatively simple. One method is illustrated on the next page. Place the infant or child prone on the examining table, on the parent's lap, or on your own lap. While you separate the buttocks with the thumb and forefinger on one hand, with the other hand gently insert a well-lubricated rectal thermometer, inclined approximately 20° from the table or lap, through the anal sphincter to a depth of approximately 2 to 3 centimeters. Keep the thermometer in place for at least 2 minutes.
Fever (>38.0°C or >100.0°F) in infants <2-3 months may be a sign of serious infection or disease. These infants should be evaluated promptly.
Body temperature in infants and children is less constant than in adults. The average rectal temperature is higher in infancy and early childhood, usually not falling below 99.0°F (37.2°C) until after age 3 years. Body temperature may fluctuate as much as 3°F during a single day, approaching 101°F (38.3°C) in normal children, particularly in late afternoon and after vigorous activity.
During early childhood, extremely high fever (up to 104°F or 40°C) is common, even with minor infections.
Anxiety may elevate the body temperature of children. Excessive bundling of infants may elevate the skin but not the core temperature.
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